Thanks for all your help guys, sailed through the MOT today with no advisories, so I'm a happy bunny.
In case anyone is looking to do the same in the future:
Genuine front discs and pads ordered from a Volvo dealer via eBay. £170 delivered. Apart from one stubborn bolt on a calliper bracket was a straightforward swap out and probably took an hour or so each side (plus an additional hour for the damn bolt).
This guide
https://www.volvoforums.org.uk/showthread.php?t=106029 from @BestGear was a great help. Now no vibration on breaking.
For the backs, again genuine discs, pads & shoes and I also added in the brake adjusters for good measure (£140 all in). Again a fairly straightforward swap out. Adjusted the shoes right up with the adjusters once the discs were on. Once everything was put back together the handbrake didn't go past 3 clicks rather than the 10 clicks previously.
It took a few days of constantly putting the handbrake on every time I stopped to scuff them up and they hold quite well now. Not enough to stop my car rolling off the drive in neutral but hey It passed the MOT so I'm happy.
As for the alarm, I replaced the fuse to clear the error and so far......
Will have to wait and see on that one.
So thanks again to everyone for their help and advice.